MODEL 330 OPERATOR'S MANUAL - Peterbilt Motors Company

Using the Brake System
vehicle. Be sure to be in the right gear before you
start down a hill, especially if you have a manual
transmission. You could get hung up in NEUTRAL
and lose the benefit of engine braking. “Coasting” is
illegal, and also VERY dangerous.
Anti-Lock Braking System
This vehicle is equipped with an Anti-Lock Braking System
(ABS). ABS reduces the likelihood of a wheel locking. If a
wheel is about to lock during braking, the ABS will automatically
adjust hydraulic pressure to the brake calipers on the
appropriate wheel(s) to prevent wheel lock-up. The ABS is
automatically activated when the ignition switch is turned on.
Hydraulic fluid from the primary and secondary master cylinder
chambers feeds the (ABS) modulator valve body. Simultaneously,
the vehicle's ABS system detects wheel speeds.
The sensors generate signals that are transmitted to an Electronic
Control Unit (ECU). If the wheels start to lock, the ECU
signals the modulator assembly to regulate the brake pressure
of each locking wheel.
Operating Instructions
WARNING! Do not replace wheels or tires with a
different size than originally installed. The Anti-
Lock Brake System (ABS) is calibrated for the
specific tire revolutions per mile. Use of a different
tire and/or wheel size may cause the ABS
system to not function during a hard braking
event. This could cause an accident or serious
personal injury. See “Wheel and Tire Replacement
for Trucks with Hydraulic Brakes” on page
182 to determine the acceptable range of tire rev/
mile.
ABS Warning Lamp
The ABS warning lamp will come on briefly, then go off, when
the key switch is first turned on. If the lamp remains ON until
a speed of 4 mph (6 km/h) is reached, then goes OFF, there
may be a stored fault code. If the lamp remains ON when a
speed in excess of 4 mph (6 km/h) is reached, there may be
an active fault in the ABS system.
CAUTION: If the ABS warning light does not illuminate
when the ignition is first turned on, there
is a problem with the bulb or wiring. You should
have this checked as soon as possible.
– 90 – PB1318 3/01 Model 330